feat: stringify bigint, addresses issue gcanti#648

src/PathReporter.ts

@@ -15,7 +15,7 @@ function stringify(v: any): string {
     }
     return v > 0 ? 'Infinity' : '-Infinity'
   }
-  return JSON.stringify(v)
+  return JSON.stringify(v, (_key: string, value: unknown) => (typeof value === 'bigint' ? `BigInt(${value})` : value))
 }
 
 function getContextPath(context: Context): string {

test/PathReporter.ts

@@ -0,0 +1,25 @@
+import * as assert from 'assert'
+import { PathReporter } from '../src/PathReporter'
+import { bigint, brand, Branded } from '../src'
+import { struct } from '../src/Type'
+
+describe('PathReporter', () => {
+  it('should properly report decoding errors against a bigint value', () => {
+    interface PositiveBigIntBrand {
+      readonly PositiveBigInt: unique symbol
+    }
+
+    const PositiveBigInt = brand(
+      bigint,
+      (n: bigint): n is Branded<bigint, PositiveBigIntBrand> => BigInt(0) < n,
+      'PositiveBigInt'
+    )
+
+    const testC = struct({ value: PositiveBigInt })
+    const testValidation = testC.decode({ value: BigInt(-10) })
+
+    const result = PathReporter.report(testValidation).join('\n')
+
+    assert.equal(result, 'Invalid value "BigInt(-10)" supplied to : { value: PositiveBigInt }/value: PositiveBigInt')
+  })
+})